Here is a rundown of the steps of the hajj, which is one of the largest gatherings in the world and closed to non-Muslims. This year's pilgrim numbers have surpassed last year's.
Because the Islamic calendar is a lunar one, the time of year when the hajj takes place varies, and when it falls in the hot summer months, temperatures can soar to over 100 F (38 C).
The second day of Haj is known as Yaum Arafah, as pilgrims leave the holy site of Mina for Mount Arafat (also known as Arafah). They gather near Jabal al-Rahmah (The Mount of Mercy).
Around sunset, pilgrims head to an area called Muzdalifa, 9 kilometers (5.5 miles) west of Arafat.
Muslims will undergo five days of religious ritual. The ritual of spending the afternoon in Arafat is known as "standing before God" (wuquf). Muslim scholars have interpreted this saying as meaning "Whoever misses the standing (in Arafat) has missed Haj".
Muslim pilgrims perform morning prayers at the Grand Mosque.
Muslims do not worship the Kaaba, but it is Islam's most sacred site because it represents the metaphorical house of God and the oneness of God in Islam.
This year 200 survivors and relatives of the victims of the March mosque shootings in Christchurch, New Zealand, that killed 51 people are attending as guests of the king of Saudi Arabia. There are two pilgrimages: the Hajj and the Umrah. It's a healing process.
"I am very happy now".
"Up to this time, I can tell you none of them came to us to explain what happened or seek for help, apart from the agent of Flynas which they approached".
"I can not express my feelings. It was an fantastic feeling".
"We have more than 8,200 group leaders that are responsible for movement of the crowds", Maddah said. As far as the state pilgrims boards are concerned, exactly 44,450 intending pilgrims registered and paid for their hajj and they have all been airlifted to the Kingdom of Saudi Arabia to perform their hajj. The Arafat sermon was delivered by Sheikh Muhammad Bin Hassan Al Al-Sheikh, member of the Council of Senior Scholars.
Pilgrims from around the world then headed on foot or on buses to Mina, a rugged district of Mecca at the base of Mount Arafat, where the faithful will spend Friday night.
The white garments are forbidden to contain any stitching - a restriction meant to emphasize the equality of all Muslims and prevent wealthier pilgrims from differentiating themselves with more elaborate garments. Finally, pilgrims will do a farewell Tawaf in Masjid-al Haram before leaving the holy land to complete their Hajj.